Textile treating process



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Nov. 9, 1943. D. J. CAMPBELL ET Al. 2,334,066

TEXTILE TREATING PROCESS Filed Aug. 50 1940 5 Sheets-Sheep 1 (12CHSTEAMING TUBE CL 0 TH l SATI'TI/G G. 77' WASHER 79 INVENTORS. DON/JLD JCAMPBELL IANCIS LEROYFENNELL ATTORNEY.

NOV. 9, 1943. D 1 CAMPBELL TAL 2,334,066

TEXTILE TREATING PROCESS Filed Aug. 30, 1940 5 Sheets-Sheet 2 INVENTORS.DONALD J. CAMPBELL IZI/ANCIS Ls OYFENNELL ATTORNEY.

INVENTORS.

FENNELL BY 'A TTORNEY.

DON/ILD J. CAMPBELL FRANCIS LE m0195011; asdzom Bu Nov. 9, 1943. D, J,CAMPBELL ET AL 2,334,066

TEXTILE TREATING PROCES S Filed Aug. 50, 1940 5 Sheets-Sheet 4 PER-CENTWHITENESS PER-CENT HaoZ coNsuMED IO ZO 30 40 50 60 TME IN MINUTESPER-CENT wmTENEss Pam-,ENT Haoa coNsuMeD 1o zo 3o 4o 5o @o TIME INMnNUTEs I N VEN TORS.

DONALD .L CAMPBELL -FRANCIS LEROYF ATTORNEY Nov. 9, 1943.

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INVENTORS. DONALD J. CAMPBELL FRANC/S LE OYFENNELL Patented Nov. 9, 1943search iiGGm UNITED STATES PATENT OFFICE TEXTILE TREATING PROCESSApplication August 30, 1940, Serial No. 354,866

8 Claims.

This invention relates to the treatment of textile goods and is acontinuation-in-part of our copending application Serial No. 264,872,iiled March 29, 1939, now Patent No. 2,267,718, issued December 30,1941.

This invention relates more particularly to the bleaching of textilefibres and fabrics, herein generally referred to as goods, utilizing asthe bleaching agent a peroxide such as an alkaline solution of hydrogenperoxide or a solution of an alkali metal peroxide.

Textile goods such as those of vegetable origin, especially such textilematerials as cotton or those consisting largely or predominantly ofcotton, are commonly bleached with alkaline solutions of peroxides.Alkaline or acid solutions of peroxides, more particularly solutions ofhydrogen peroxide or of an alkali metal peroxide such as sodiumperoxide, are also customarily employed in the textile bleachingindustries to a large extent for bleaching other textile fibres such asthose fabricated from regenerated cellulose, acetate rayon, silk, linen,wool, and other bres of animal or vegetable origin. Our inventionrelates to a new and improved process utilizing solutions of peroxidessuch as an alkaline solution of hydrogen peroxide for the bleaching oftextile fibres, more especially those of vegetable origin.

Our process has for its primary aim the bleaching of such textile` bresunder conditions wherein there is less degradation of the chemicalnature of the textile fibre, more constant and uniform bleaching, andless unevenness in the bleaching action. In addition to theseadvantages, which result in the securement of a bleached textile fabrichaving superior dyeing qualities, our method possesses the importantcharacteristic of insuring the production of a higher degree ofwhiteness in the bleached textile fabric for equal quantities ofperoxide than was ever before attainable in commercial bleachingmethods. This aim or advantage may also be expressed by stating that bythe use of our improved bleaching process it is possible to produce agiven degree of whiteness in bleached textile fabrics with theconsumption of a lesser quantity of peroxide.

Various methods for bleaching textile goods by the use of the peroxidesare now known and employed to a greater or less extent in commercialble-aching operations. Among these methods the kier bleaching methodhas, in the past, been utilized to perhaps a greater extent than othermethods.

In the kier bleaching method wherein textile fabrics are bleached withalkaline solutions of hydrogen peroxide, the fabric is packed in a kierand the lid is securely closed. A solution of caustic soda is thencirculated through the cloth for eight to twelve hours. The temperatureis ordinarily about 250 F. 'and the gauge pressure 15 lbs. At the end ofthis period the goods are washed with fresh water. This washing may beconducted in the kier or the cloth may be withdrawn and Washed inseparate equipment and reloaded into the kier. After Washing the fabricsare treated for 4 to 6 hours with an alkaline peroxide solution at atemperature of 180 to 200 F.

While kier bleaching methods have generally produced satisfactorybleaching results, they possess certain disadvantages. Since arelatively long time is required for the treatment, expensivepressure-sustaining equipment must of course be used. But perhaps themost important disadvantage of kier bleaching methods is that thecomparatively rigorous treatment necessary to effect satisfactorybleaching of the textile fabrics results in considerable degradation.

The chief advantage of employing a high temperature during bleachingoperations wherein alkaline solutions of peroxides are employed is therapidity of bleaching action secured with the elevated temperature. Butwhile high temperature bleaching is rapid, there is a distinct tendencyto unevenness in bleaching unless a comparatively even temperature isquickly secured. Moreover, textile libres are extremely sensitive to theaction of alkaline agents at high temperatures and if the treatment iscontinued too long at the elevated temperature, serious degradation ofthe textile libres occurs.

In kier bleaching operations the necessity for prolonging the bleachingtreatment to periods ranging from eight to twelve hours, in some caseseven overnight treatments, is occasioned by the difficulty of bringingall the goods in the kier up to the bleaching temperature and treatingthe fabrics therein evenly with the bleach liquor. While most of thebleaching in a kier employing alkaline solutions of hydrogen peroxide asthe bleaching agent may be accomplished in a period of as short durationas two ho-urs, in order to secure evenness of bleach the treatment mustbe continued for a total bleaching period which may be twelve hours ormore. This continuance of the heat input after the goods have beenpacked into the kier and after the major portion of the bleaching hasbeen completed, necessary to secure thorough penetration and bleachingof all parts of the fabrics, results in an uneven treatment in- Sofa? asthose portions of the fabric which have been bleached to a substantiallycomplete whiteness are concerned. The necessity for continuing the heatinput for some six to ten hours after most of the bleaching has takenplace overtreats or degrades those portions of the fabrics rst bleached,i. e., those receiving the treatment with the alkaline agents at theelevated temperature over the longer period. This unevenness of actionis characteristic of kier bleaching, and the resulting degradation ofthe fibre not only causes variations in the degree of whiteness butcauses unevenness of dyeing in that one part of the bleached cloth has amore uniform and greater affinity for dyestuffs than have other portionsof the fabric.

In the past these disadvantages of kier bleaching have been recognizedand various processes have been proposed in an effort to avoid thedifficulties of this bleaching method. Among such processes are thosewherein the textile fabric to be bleached is rst impregnated with thebleaching solution and then stored, in contact with a source of heat butout of contact with the bleach liquor, for a period of time sufcient toeffect bleaching. While possessing advantages over kier bleaching inseveral particulars, chief among which are perhaps the possibility ofavoiding the circulation of large quantities of alkaline bleach liquorthrough the kier and the resulting superiority of the bleached fabricbecause it has not been brought into repeated contact with the boilinghighly alkaline bleach liquor, such methods have not completely avoidedthe disadvantages previously enumerated.

In such methods the textile fabric to be bleached is ordinarily wet outin the bleach liquor and the fabric then stored in a closed chamberwherein it is brought into contact with the source of heat, usuallysteam at atmospheric pressure or at a pressure above atmospheric. Duringthis period the goods are heated by the heating medium and a hightemperature is sustained by the constant and continued heat input forthe period necessary to effect the desired bleaching. Unfortunately,this continued heat input, necessary in such processes to securesatisfactory action of the bleach liquor on the goods, results incertain objectionable disadvantages. Thus, the continued heatingsubjects certain portions of the fabric to more heat than other portionsand so results in unevenness of treatment. This uneven characteristic isparticularly pronounced where the goods are stacked by means of someform of stacking device in the heat chamber in the form of folds, thoseportions of fabric adjacent the folds and in contact with the stackingdevice through which heat is continuously supplied being subjected tomore rigorous heat treatment than portions intermediate to the edgeportions and positioned more centrally in the folds of the stackedfabric. This unevenness, due to continued heat input and irregular heattreatment, not only results in certain portions of the fabric beingbleached to whiteness percentages diiTerent from those of other portionsof the fabric, but also results in increased fibre degradation whichshows up as uneven dyeing when the bleached goods are subsequentlysubjected to the dyeing operation.

In such processes the cloth wet out with the bleaching liquor losesweight during the heat treatment, i. e. there is evaporation or loss ofmoisture or bleaching liquor from the textile fabric. We have found thatthis drying out action is objectionable, and gives rise to a tendency tobring about scorching or incipient scorching of the fabric. In ourprocess no such loss in weight occurs, the goods having a greater Weightat the end of the process than after having been impregnated with bleachliquor at the start, due to condensation of steam thereon during ourbrief heating step.

Accordingly, it is one of the objects of this invention to provide animproved method for bleaching textile fabrics with alkaline solutions ofperoxides whereby the necessity for providing a continued heat inputthroughout the bleaching period is avoided. The attainment of thisobject results in more even bleaching, lower degradation of the bleachedbre, and a more uniform aiiinity of the fabric to dyestuffs where thefabric is to be subsequently subjected to a dyeing operation.

Another object of this invention is to secure a given degree ofwhiteness with lower peroxide consumption and therefore lower cost forthe bleaching agent required than necessary when employing those methodsrequiring continued heat input characteristic of the prior art. Thisobject may also be expressed by stating that it is our aim to securewith equal amounts of peroxide a higher degree of bleaching thanpreviously possible with methods wherein the fabric is contacted with asource of heat such as boiling bleach liquor or steam throughout thebleaching period. These and still further objects of our invention willbe apparent from the ensuing disclosure of certain improved embodimentsthereof.

In our process the goods to be bleached are saturated or padded with analkaline bleach solution such as an alkaline solution of hydrogenperoxide having a pH value falling within the range 8.0 to 12.0.Generally the alkaline peroxide solution employed will contain one ormore alkaline agents such as caustic soda, soda ash, caustic potash,tri-sodium phosphate, borax, or water-glass (sodium silicate) Since mostof the peroxide bleach baths commercially utilized contain sodiumsilicate, the pH of such solutions usually falls within the somewhatnarrower pH range 10.0 to 11.0. y

The goods to be bleached may be readily impregnated with the bleachliquor by running the fabric, which ordinarily will have been previouslysubjected to the usual preliminary boil-out or alkaline scour treatment,through the alkaline solution of hydrogen peroxide or other peroxidesolution selected and then through squeeze rolls to squeeze out excesssolution. The scouring of the goods with alkaline agents may have beenpreviously carried out in accordance with the process of our copendingpatent application, or other usual boil-out or scouring processes may beemployed. Under certain circumstances certain types of goods may bebleached without preliminary caustic treatment.

The impregnated goods, which may contain an amount of bleach liquorapproximately equal in amount to their own weight, are then contactedwith a source of heat such as steam by being passed through a steam tubefor a brief period of time. Here the wetted cloth is heated rapidly toan elevated temperature which, when steam at the atmospheric boilingpoint is employed, will be substantially 212 F. or some temperatureclose thereto, ordinarily 200 F. or higher. The heated material is nowstored in a compartment under conditions wherein loss of heat from theheated fabric is hindered by providing suitable heat insulation aroundthe compartment. However, no continued heating is carried out, and thereis no heated medium of any sort provided for continuing the heat inputto the fabrics. Under the usual conditions of insulation and where thegoods have been heated to a temperature of close to 212 F. by momentarypassage through the steam chamber before storage in the bleachingcompartment, the temperature of the fabrics will ordinarily fall from atemperature of approximately 200 F. to one in the neighborhood of 170 F,during the ensuing bleaching period of approximately sixty minutesduration,

Accordingly, our process may be most simply described as involving thesteps of rst thoroughly impregnating the goods to be bleached with thebleach liquor, generally an alkaline solution of a peroxide such ashydrogen peroxide. The excess bleach liquor is then removed and thegoods passed rapidly through a chamber filled with steam, where they arerapidly brought up to a temperature substantially in the neighborhood of212 F. The goods are then stored in a storage apparatus which in textilemills may most conveniently be in the form of a J-box. This J-box isgenerally provided with stacking means at its upper portion and the webof fabric is stacked by the stacking means in order to fold it compactlyinto the storage space. At the conclusion of the stacking operation thetemperature of the fabric web will ordinarily be very close to 200 F.Owing to the fact that the storage compartment is insulated, thetemperature will be maintained to a substantial extent during theensuing period but will nevertheless slowly and regularly decrease to atemperature of approximately 170 F. at the end of a bleaching period ofone hour.

Our process does not require the provision of a heated medium during thestorage period, and the addition of heat to the stored goods by means ofa heated medium is definitely to be avoided, as we have discovered thatsuch continued heat input is objectionable, and in fact constituted oneof the major difliculties in the bleaching methods as now known to theart.

Preferably our process is carried out in a continuous manner, thetextile fabric to be bleached being treated either in the form of ropeor web and, preferably, in continuous lengths. The goods in continuouslengths may therefore be passed through a saturating vessel containingthe alkaline solution of the bleaching agent and then continuouslypassed through a squeeze roll or a wringer for removing the excessbleach liquor. The web is then passed through the steaming compartmentwherein it is subjected to the action of steam at substantially theatmospheric boiling point of water (212 F.) After this rapid rapidheating to a temperature closely approximating that of the steam, thelength of goods is passed into the storage compartment through which therate of travel is adjusted to provide adequate time to permit action ofthe alkaline bleach bath to effect the desired bleaching action on thegoods As generally carried out, we prefer that this period of time be inthe neighborhood of one hour, although under some circumstances periodslonger than this may be employed. It is also within the scope of ourinvention to utilize storage periods of less than one hour, storageperiods as brief as thirty minutes having been found satisfactory undercertain circumstances.

The stacked goods in the storage compartment are readily andcontinuously withdrawn from that compartment after having remainedtherein the desired length of time. As previously pointed out, thestorage compartment should preferably be insulated against excessiveheat loss so that the temperature of the goods which at the beginning ofthe bleaching period is 200 F. or close thereto should be at atemperature within the neighborhood of F. at the time of their removalfrom the storage compartment at the end of our preferred storage periodof approximately one hour. After removal from the storage compartmentthe fabrics may be washed and are then ready for subsequent utilizationfor textile purposes. Washing may, of course, be followed by or includescouring or any other treatment applied to textiles subsequent tobleaching.

Our invention and the advantages resident therein over the bleachingprocedures as now known to the art may perhaps be better understood fromthe annexed drawings. In the drawings Figs. 1 through 6 representdiagrammatically and in detail one form of apparatus adapted forcarrying out the herein-described process of bleaching textile fabrics.Figs. 7 through 15 are graphs illustrating the theoreticalconsiderations involved in our process wherein heat input, after initialheating, is avoided during the period wherein the goods are allowed tostand in contact with the bleach liquor.

Referring particularly to Figs. 1 through 6, Fig. 1 is an elevationalview, certain parts being cut away so as to show various internaldetails, of one form of apparatus adapted for use in practicing ourprocess. Fig. 2 is a vertical sectional view of the apparatus of Fig. 1with a few modifications which are pointed out fully in the followingdescription. Fig. 3 is a cross-sectional view of the steaming tube ofFigs. 1 and 2, taken on the line 3 3 of Fig. 2. Fig. 4 is a verticalcross-sectional view of a modification of the apparatus shown in Fig. 2,only the upper part of the apparatus being shown. Fig. 5 is a verticalcross-sectional view of the steaming compartment of Fig. 4, taken alongthe line 5-5 of Fig. 4. Fig. 6 shows diagrammatically the various piecesof equipment including a saturating vat and a washer, for carrying outour improved process of bleaching including the step of washing thetreated goods after they emerge from the storage compartment.

Referring to Figs. 1 and 3, I is a box constructed in the sha-pe of a Jand which will be referred to hereinafter as a J-box. This J-box isprovided at its upper end with a steaming or heating tube 2 havingapertured end caps 3. Tube 2 is also provided with steam inlets 4through which jets of steam are introduced into tube 2. The manner ofattachment of steam inlets 4 to tube 2 so as to provide tangential jetsof steam will be more apparent from the arrangement of inlets 4 withrespect to tube 2 as shown in Figure 3. Tube 2 is further provided withdrain tube 5 for the escape of steam and condensate and also with athermometer well S. The cloth rope which passes through steam tube 2 andinto the J-box is indicated generally by the numeral 7. Caps 3 areprovided with apertures 8 through which cloth rope 'l passes. Afteremergence of cloth rope 'l from steam tube 2 it passes through drawrolls il which serve as means for drawing the cloth through the steamtube. The J-box is provided with a lower hinged cover Il having openingl2 therein through which the cloth is withdrawn from the J-box by meansnot shown in the drawings and also with an upper hinged cover I0. Thelowest portion of the J-box is provided with a drain tube I3 havingvalve I4 therein.

The apparatus of Figure 2 differs slightly from that of Figure 1 in thatin place of squeeze rolls 9 there is provided a stacking means forstacking the cloth rope in a loose and orderly manner in the J-box. Thisstacking means consists of a winch I8 which cooperates with travellingeye guide I9, so as to stack the cloth rope in a manner conformingroughly to the cross-sectional shape of the vertical portion of the box.Winch I8 is caused to travel back and forth across the top of the J-boxas indicated generally by the arrows and the numerals I8 and IBa. Eyeguide I9 travels backward and forward horizontally in a direction atright angles to the direction of travel of winch I8. Any suitable meanscommonly employed for such purpose may be used for effecting the desiredmovement of winch I8, no such means being shown in the drawing. Eyeguide I9 is supported on travelling support 29, the latter being causedto travel back and forth upon track 2I by means of worm 22. It isevident that by coordinating the movements of eye guide I t* and winchI8 the cloth rope, as it emerges from steam tube 2, may be stacked in aloose and orderly manner in the J-box. Aside from its function instacking the material in the J-box, Winch I3 serves to draw the clothrope through steam tube 2 and thus functions in the same manner as doesthe pair of squeeze rolls 9 in the apparatus of Figure 1.

The apparatus of Figure 2 also differs from that of Figure 1 in thateach cap member 3 is provided with an inwardly extending annular portionI5 whose inner end IB is flanged centrally with respect to annularportion I5 so as to provide openings I'I. In this modification each capmember 3 provides two openings, indicated by the numerals 8 and I'I,through which the cloth rope passes, which arrangement provides betterassurance against excessive loss of steam through the openings providedfor the travel of the cloth. It should be remarked, however, that inneither of the modifications shown in Figure 1 and Figure 2 do theopenings in the end caps 3 provide an absolute seal against passage ofsteam therethrough. However, in normal operation of the apparatus butlittle steam will pass yfrom steam tube 2 into the top of J-box I.

The apparatus illustrated in Figures 1 and 2 functions to heat the clothin rope form rapidly to a temperature approximating that of thetemperature of steam at atmospheric pressure and then permits thestorage of the heated material initially saturated with the alkalinebleach liquor solution in a storage compartment for a predeterminedlength of time. Since an interval of only a fraction of a second, or atmost no more than a few seconds, is required to heat the cloth by meansof steam in accordance with our invention, it is apparent that the timerequired for the bleaching will correspond substantially to the time thecloth is maintained in the storage compartment, which time may beregulated as desired.

Since storage of the saturated and heated textile fabrics in the storagecompartment should be carried out under circumstances wherein thetemperature of the cloth varies from substantially 200 F. to 170 F.during the one hour period wherein the goods are in the storagecompartment, the J-box I is preferably insulated in order that thetemperature may be thus regulated. However, as previously emphasized, nosource of heat is supplied to the J-box, nor are any portions of thefabric subjected to the action of any heating medium at any time duringthe storage. We have found that a J-box consisting of a wooden shell,shown as element 23 in Figure 2, provides adequate insulation againstheat losses so that the temperature does not dro-p below about F. in thecloth leaving the J-box through opening I2 at the end of the one hourstorage period. However, other insulating media may of course besupplied. In its preferred form the J-box may be provided with an innermetal lining 2li, which exposes a smooth surface to the cloth and whichis preferably made of a corrosionresistant metal such as stainlesssteel.

Instead of a cylindrical steaming tube such as element 2 of Figures 1and 2, a steaming tube of rectangular shape may be employed as shown inFigures 4 and 5. In the latter gures a rectangular shaped steam box 50is provided with a plurality of steam inlets 5I and with steam andcondensate outlet 52. Steam inlets 5l are preferably provided with bafeplates 56 adapted to prevent direct impingement of the incoming steamupon the cloth. Numeral 53 indicates a thermometer Well. The ends ofsteam box 59 are provided with slots 54 through which cloth strips 55may be passed in open width. Steam box 59 is preferably built integralwith the upper part of a J-box 5l or other suitable storage compartment.Only the upper part of the storage compartment 57 is shown, which partis provided with a hinged cover 58 and consists of an outer wooden shell59 having an inner metal lining 69, as is the case in the apparatus ofFigure 2. The length of open width cloth 55 is drawn through steamchamber 59 by means of winch 6I which is provided with means not shownfor moving the winch back and forth across the top of the box, e. g.,between the positions 5I and Sia as indicated by the arrows. It is seenthat Winch 5I has two functions, i. e., to draw the cloth through thesteaming compartment and also to stack the cloth in the storagecompartment.

Whether or not the apparatus of Figures 1 and 2 or that of Figures 4 and5 should be employed will depend upon the cloth being treated and alsoupon the uniformity of the results desired. The apparatus of Figures 4and 5 permits the passage of cloth in open width form through theapparatus which facilitates a more rapid and uniform heating of thegoods. This may be desirable in some circumstances. In general, however,excellent and uniform heating may be obtained using the cylindricalsteaming tube of Figures 1 and 2. Results of practical trials haveindicated that With cloth rope of l/g inches in diameter substantiallyinstantaneous and uniform heating to the desired temperature is readilyobtained.

A schematic diagram of assembled apparatus for use in carrying out ourprocess as described is illustrated in Figure 6. As shown in thedrawings, the textile fabric in continuous length is caused to travelthrough a saturating bath con.- taining the alkaline bleaching liquor.The cloth is then passed through the steaming tube into the J-box, afterwhich it is passed through a washer. The washer may be of any typeconventionally utilized in textile treating processes. Prior to passagethrough the saturating bath the cloth strip may be drawn through guideeye li, which shapes the strip into the form of rope 79. However, aspreviously indicated, the bleaching may be carried out in open width, inwhich case suitable rollers (not shown) will take the place of the guideeye. The cloth passes into the saturating solution and under guide rolls12 located therein. Squeeze rolls 13 express excess bleaching liquorfrom the saturated goods and the guide 14 serves to direct the clothrope into the steaming chamber through which it then passes into thestorage compartment. The treated fabric may be withdrawn from the J-boxstorage compartment by means of winch 15 after having passed over guiderolls 16. From winch 15 the cloth passes through the washer, which mayconsist of the three washing compartments indicated by the numerals 11,18, and 19. Washing com-y partment 11 may contain a soap compound,washing compartment 18 a hot water rinse, and washing compartment 19 acold water rinse. The washer is indicated generally as including twolong squeeze rolls 80, through which the cloth rope 10 is threaded so asto cause loops of rope to dip a number of times into each washingcompartment prior to emergence from the washer. Other types of washersmay be employed, and instead of the particular washing solutionsindicated, other solutions such as a souring solution, may be used inone or more of the washing compartments.

Cloth rope 1, while passing through apertures 8 in end plate 3 of Figure1 or apertures 8 and I1 of Figure 2 functions as a seal to preventexcessive escape of steam from the ends of the steam tube. Cloth rope 55acts in a similar inanner in preventing escape of' steam from slots 54in the end walls of steam chamber l: of Figures 4 and 5. It should benoted that the steam chamber in all of the modifications of theapparatus illustrated in the drawings is at all times open to theatmosphere so that the steam in contact with the goods is never at atemperature higher than substantially the atmospheric boiling point ofwater. This means that the cloth is never heated to a temperature abovethat temperature. We have discovered that the cloth may be heatedrapidly and substantially uniformly in this manner when a steam tube ofsufficient length is utilized. For fabrics of normal weight a cloth ropeof about 1.5 inches in diameter may be effectively heated tosubstantially the temperature of steam at atmospheric pressure duringpassage through a steam tube approximately 6 inches in diameter and 6feet long when passage through the tube is at a rate of 100 to 150 yardsper minute. In

general adequate heating of the continuous length of cloth will beaccomplished if the rate of travel of the goods through the steam tubeis such that a given point of the strip will be contacted with the steamfor a period of time on .the order of one second. This time intervalobviously may vary considerably depending upon the type of goo-ds beingtreated and other obvious factors, but rarely will a period longer thanabout 1 to 10 seconds be required.

Apertured end cap members 3 of Figures 1 and 2 constitute in effectconstrictions of the steaming tube 2. Instead of the structure shownconsisting of these end caps, the steaming tube of our apparatus may be"constricted in any desired manner so as to provide openings thereincorresponding to apertures 8 and I1 through which the continuous lengthof goods passes so as to provide an effective seal against excessiveloss of steam at the points of constriction. Constriction at the desiredpoint may be accomplished merely by shrinking the diameter of the tube,by inserting apertured plugs into the tube, or by any other equivalentmanner. Instead of a simple steaming tube with steam inlets and outletsas shown ih the drawings, the walls of the tube may be perforated andprovided with an outer `iacket into which the steam is initially passed.Ubviously the number oi` steam inlets and/ or steam outlets employed maybe varied as desired. Still other modifications of the apparatus will beobvi'ous to those skilled in the use of apparatus for treating textilematerials.

Our process is capable of utilization with bleaching liquors of varyingstrengths and cohtaining va.ying amounts of peroxygen compounds or otherbleaching agents. Generally we prefer to use an alkaline solution ofhydrogen peroxide, although other peroxygen compounds such as sodiumperoxide or sodium perborate may be effectively utilized under certaincircumstances. 'lhe concentration of peroxide in the bleach bath mayrange from 1 volume or even below 1 volume to concentrations of 2volumes or greater. 'lhe volume concentration ci' a solution of hydrogenperoxide or other peroxygen compound is defined as the number of'volumes of oxygen gas measured at 0 C. and 160 mm. of mercury pressurethat will be released from one volume or' the solution at 20 C.Commercial solutions of hydrogen peroxide such as those sold under thetrade-mark name Albone are of 10U volume concentration and containsubstantially 21.6% H2O2 by weight and approximately 30% H2O2 by volume.Such solutions are ordinarily diluted by the addition of water in orderto give the desired concentration. They are also usually renderedalkaline by the addition of various alkalizing agents, such as causticsoda, caustic pot'ash, soda ash, sodium peroxide, etc. Usually, astabilizing agent is present in the commercial solution of hydrogenperoxide used to prepare the bleach bath, and under some circumstancesone may be added to the bleach bath itself. Usually commercial bleachbaths contain sodium silicate, which operates both as a buffering agentto maintain the pH within a desired range and also as an alkalizingagent. Our preferred bleach baths may therefore be described as alkalinesolutions of peroxide which may contain from 1 to 6% and preferably from1 to 4% of caustic soda or its equivalent. Peroxygen salts, such assodium perborate, may also be utilized. The bath will preferably havxe apH falling within the range 10 to 12 and will contain hydrogen peroxideor equivalent peroxygen compound in amount corresponding to 0.3% to 0.6%by weight. The use of such baths will produce, when utilized inaccordance with our process wherein heat input during the storage periodis carefully avoided, highly uniform whiteness in the bleached fibre,-as well as a fabric with a high degree of absorbehcy. Under somecircumstances the bleach bath may contain a wetting agent in order tofacilitate rapid wetting of the fabric with the treating solution,although such an agent is ordinarily not necessary. After the goods arewetted out in the bleach bath and excess bleach liquor expressedtherefrom, they will normally contain an amount of bleach liquorcorresponding roughly to from to 150% by weight based on the weight ofthe fabric itself. However, great-er or lesser quantities of thetreating liquor may be retained in the goods, depending upon theparticular quality of bleaching desired and upon the strength of thebleaching liquor.

It will also be evident that our method is not restricted to a method ofoperation wherein the goods are'passed but once through the saturatingbath and storage compartment, as it may be desirable in certaininstances to subject the goods to a plurality of treatments in whichsuccessive treatments may be the same or may vary somewhat' as to theconcentration and character of the bleach bath applied. The goods beforetheir subjection to bleaching may have been previously boiled out inaccordance with standard scouring operations, either those previously inuse by commercial bleachers, or in accordance with that described in ourpreviously referred to copending patent application. Thus the advantagesof both procedures may be secured. Under certain circumstances priorscouring or treatment with alkaline agents may of course be eliminated,and the use of our process for bleaching textile goods which have notbeen previously subjected to the action of such alkaline agents is ofcourse within the contemplation of this invention.

The advantages of our process wherein heat input is avoided during theperiod wherein the goods to be bleached are maintained in contact withthe bleaching liquor may be particularly illustrated with reference tothe graphs shown in Figures'7 through 15 inclusive. These graphs show,in particular, the advantages of carrying out our process so that thecloth to be bleached is quickly brought to the necessary hightemperature, one of substantially 212 F. or one somewhat below thistemperature, and then stored under conditions such that the temperatureof the cloth varies from substantially 200 F. to 170 F. during thestorage period. These graphs show the superiority as a bleaching processof our process over those wherein heat is supplied by contacting aheated medium, usually steam, with the impregnated cloth in order thatthe cloth may be maintained at a substantially constant temperatureduring its period of storage. Specically, the curves sho-w theadvantages of rapidly heating the cloth in the steaming tube bycontacting it with steam at substantially atmospheric pressure and thenstoring it out of contact with any heating medium, over processeswherein a heating medium such as steam is continuously present tomaintain the temperature of the fabric at 212 F., or at temperatureslower than 212 F., such as 170 F., during the storage period. In allcases the storage period is substantially one hour, which is thepreferred storage period in our process, and this may be dened as theperiod during which the cloth is in contact with the bleach liquor underconditions wherein bleaching can take place.

Specifically, the graphs of Figures 7 through 10 show that it ispossible to secure a higher percentage of whiteness at the same peroxideconsumption, or to secure the same percentage of whiteness with a lowerperoxide consumption, when no heating medium is supplied and thetemperature is allowed to drop from 200 to 170 F. throughout the storageperiod than when a heating medium such as steam is supplied and thetemperature maintained at 212 F. or some temperature below 212 F. suchas one of 170 F. throughout the entire storage period.

The graphs of Figures 11 through 13 inclusive show the greater rapidityof the bleaching action when the temperature varies from 200 to 170 F.during the storage period, as contrasted with those methods wherein aheating medium is supplied to keep the temperature constant during thestorage period. This greater rapidity of bleaching results in a higherdegree of whiteness after a given time interval with the process hereindescribed as compared with those wherein heating media are continuouslysupplied. These curves also show the amounts of hydrogen peroxideconsumed, in the two methods, plotted against the duration of thebleaching period.

The curves of Figures 14 and 15 are designed to show the lesseneddegradation in the textile fibres characteristic of our improved methodwherein the temperature of the fabric during storage varies from 200 F.to 170 F. as contrasted with the bre degradation where a heated mediumis supplied to maintain the fabric at a constant temperature. All ofthese curves will now be discussed in detail.

In the graphs of Figures 7 through 10, percentage whiteness is plottedagainst peroxide consumption in milligrams of H2O2 per yard of clothbleached. The whiteness determinations were made with a standardwhiteness comparator. The graph of Figure 7 shows the results utilizinga peroxide bath of 1/4 volume concentration; that of Figure 8 a peroxidebath of 1/2 vo-lume concentration; that of Figure 9 a bath of 1 volumeconcentration; and that of Figure 10 a bath of 2 volume concentration.In Figures 7 and 8 the curve marked A represents the curve obtained,plotting whiteness against peroxide consumption, for a process in whicha heating medium, steam under atmospheric pressure, was supplied duringthe storage period in order to maintain the temperature of the goodsconstantly at substantially 212 F. Curve B represents the curveresulting, plotting peroxide consumption against percentage whiteness,when the goods are treated in accordance with our improved process, noheating medium being supplied during the storage period, the temperaturefalling from 200 F. to 170 F. during the one hour storage period. It isevident in the cases of bo-th the l@ volume bleach bath and the 1/zvolume bleach bath that the method of curve B gives a higher percentageof whiteness for a given peroxide consumption than the method o1 curveA. Conversely, for a given percentage whiteness the method of curve Buses up less peroxide.

In the graphs of Figures 9 and 10 there are plotted, in addition tocurves corresponding to curves A and B, curves C and D. Curve Cconstitutes a graph of percentage whiteness against hydrogen peroxideconsumed in milligrams per yard of cloth when the temperature of theimpregnated cloth during the storage period is maintained atsubstantially 190 F. by contacting it with steam under a pressure lowerthan atmospheric as a heat source. In Fig. l0, curve D is a graph ofpercent whiteness against peroxide consumption in milligrams of H2O2 peryard of cloth when the cloth after impregnation, is maintained duringthe storage period at a temperature of F. by continuously contacting itwith steam under reduced pressure as a heat source. On each graph, thatof Figure 9 and that of Figure 10, the curves A and B are the same asthose of Figures 7 and 3, i. e. percentage whiteness is plotted againstperoxide consumption for a process wherein the temperature iscontinuously maintained during the storage period by steam at atemperature of 212 F., and a process wherein no heating medium issupplied and the temperature during the storage period varies from 200to 170 F. The latter, as shown by curve B in all of these graphs, is theimproved process described herein.

It will be apparent that in all cases the method of curve B gave ahigher percentage whiteness for equal peroxide consumption than eitherthe method of curve A or the method of curve C. For equal percentagewhiteness the method of curve B required a lower peroxide consumptionthan either the method of graph A or the method of graph C. These curvesconclusively show that the process wherein no heating medium is suppliedand the temperature is permitted to drop from 200 to 170 F. during theperiod of storage is considerably more economical and produces betterbleaching results at lower peroxide consumption than do those methodswherein a heating medium is supplied in order to maintain thetemperature of the impregnated cloth substantially constant over theentire storage period.

Referring now to the graphs of Figures 11, 12 and 13, these graphs showthe curves resulting when whiteness and peroxide consumption are eachplotted against bleaching time. The graph of Figure 11 shows the resultsobtained with a bleaching bath comprising hydro-gen peroxide ofsubstantially 1/4 volume concentration. The graph of Figure 12 shows theresults secured with a bleach bath of 1 volume concentration, while thegraph of Figure 13 constitutes a plot of the results secured with ahydrogen peroxide solution of 2 volume concentration.

In each case curve E on the percentage whiteness curve and curve E onthe hydrogen peroxide consumption curve represent the graphs resultingwhen the process carried out is that described in this application, noheating medium being supplied to keep the impregnated goods at aconstant temperature during the storage period, which temperaturetherefore drops from substantially 200 F. to 170 F.

Curve F on the percentage whiteness graph and curve F' on the hydrogenperoxide consumption graph are the curves resulting when a constantsource of heat is supplied to the sto-red goods, steam at atmosphericpressure, in order during the bleaching period continuously to maintainthe temperature at substantially 212 F. Finally, curve G on thepercentage whiteness curve and curve G on the hydrogen peroxideconsumption curve also sh-ow the results secured when a constant sourceof heat is supplied to the impregnated goods during the storage period.However, in this case the temperature maintained by the use of steam atreduced pressure during the entire storage period was 170 F. It will benoted that in the case of the graph of Figure 11 no curves correspondingto G or G were plotted.

The graphs of Figures 11 through 13, particularly curves E, F, and G,show conclusively the higher percentage whiteness attained for ableaching period of any specified duration when practicing the processherein described, as contrasted with processes wherein heat sources aresupplied to maintain the temperature substantially constant throughoutthe storage period. For all practical bleaching periods, i. e. bleachingperiods ranging from ten minutes to sixty minutes, the superiority ofthe process wherein the temperature drops from 200 F to 170 F. duringthe storage period is evident.

Referring particularly to the peroxide consumption curves on the graphsof Figures 11, 12 and 13, curves E', F', and G', it will be noted thatthe amount of peroxide consumed in a given time was always greatest whenthe temperature was continuously maintained during the storage period bymeans of a heating medium at substantially 212 F. While the amount ofperoxide consumption during a specied time interval of bleaching periodwas somewhat greater when the temperature fell from 200 to 170 F., as inour improved process, than it was when the temperature was continuouslymaintained at F. during the bleaching period, it is evident that thedifference between these two curves, curves E and G', was indeed veryslight. When contrasted with the percentage of whiteness secured(compare curves E and G) the superiority of the process hereindescribed, even though it does conf sume slightly more hydrogen peroxidein a given bleaching period, will become immediately evident.

That less degradation occurs when, after initial heating, no furtherheat input is supplied and the temperature of the stacked goods duringthe storage period is allowed to drop from substantially 200 F. to 170F., is illustrated by the results plotted in Figures 14 and 15. In thesefigures, the curves resulting from plotting the data obtained from testson cotton fabrics bleached in accordance with the method of ourinvention are represented by the letter R. The letter S, in each graph,represents the plots of the corresponding results obtained in a processwherein the cotton goods, impregnated with the bleaching solution, weremaintained at a temperature of substantially 212 F. by constantlysupplying to the stacked goods a heating medium in the form of steam atatmospheric pressure.

Figures 14 and 15 constitute a plot of fluidity in recipoises againstpercentage ci whiteness. Samples of cloths bleached to variouspercentages of whiteness by the two processes were taken and thefluidity of each sample determined. Then the uidity of ea-ch sample wasplotted against percentage whiteness to give the curves shown in Figures14 and 15. In the case of Figure 14, the samples were bleached with ahydrogen peroxide solution of 1 volume concentration, while in the caseof the curve shown in Figure 15 the bleach bath was of 2 volumeconcentration.

In determining the fluidity, the viscosity of a cuprammonium solution ofthe sample was determined in accordance with standard methods usual inthe textile bleaching industry. The fluidity, in reciprocal poises orrecipoises, is the reciprocal of the viscosity, which is normallyexpressed in poises or centipoises. Samples having lower fluidity wereless degraded and the iibre had undergone less chemical change than inthe case of those samples having higher uidities.

It is apparent from the graphs of Figures 14 and 15 that curves R, inboth gures, represent lower fluidities for given percentages ofwhiteness than do curves S. This means that for a given percentage ofwhiteness the cotton fabric is less degraded and less changed inchemical composition, i. e. less damaged, by utilizing for bleaching itthe process described herein, than it is by utilizing a constanttemperature process wherein heat is continuously supplied during thestorage period to maintain substantially constant the temperature of thestacked fabrics. Conversely, for equal fluidities, representing equalamounts of degradation and chemical change in nbre structure, i. e.,equal amounts of textile injury, the percentage whiteness is greaterwith samples bleached in accordance with the method herein describedthan when those Samples are bleached with the constant temperature heatmethods.

Since the percentage whiteness to which any given fabric may be safelybleached in commercial bleaching operations depends entirely upon thepermissive degradation or loss in tensile strength, it is significantthat by utilizing the method herein described it is possible to bleachthe fabric to a higher degree without carrying degradation and chemicalchange beyond permissive limits. This advantage of our method, whereinthe temperature is permitted to drop from 200 F. to 170 F., renders themethod much more attractive for commercial bleaching than constanttemperature methods such as those previously used in the prior art whichare, in all cases, characterized by greater amounts of fibre degradationif an equal degree of whiteness is to be secured.

It may be advantageous in some instances to utilize for padding,wetting, or saturating the goods to be bleached a bleaching solution attemperatures somewhat above room temperature. However, for most purposesthe bleaching solution in which the goods to be bleached are wet out orimpregnated will have a temperature of room temperature or even belowroom temperature, at which temperatures the bath is more stable than atelevated temperatures. This is of course an added advantage of ourmethod, for instead of having to heat the entire body of bleachingliquor to an elevated temperature as in former bleaching methods, themajor portion of the bleach liquor may be maintained at a temperature atwhich it is relatively stable, and only that portion actually in contactwith the goods and serving to eiiect bleaching need be heated to anelevated temperature. This heating to an elevated temperature is readilyaccomplished by passing the goods through a steaming tube for a shortperiod prior to stacking the goods under conditions wherein thetemperature drops from substantially 200 F. to 170 F. during the ensuingstorage period of approximately one hour.

It will be evident to those skilled in the art of treating textilematerials that various modiiications of our process and apparatus asdescribed above may be devised without departing from the spirit andscope of our invention. Thus, various means may be employed for removingexcess treating liquor from the saturated goods, and various means maybe used for zig-zagging the cloth rope in the J-box during the stackingoperation. Further, many modifications may be devised in the details ofthe process described as our preferred embodiment which wouldnevertheless come within the purview of our invention.

It may be pointed out that the apparatus including the steaming chamberis not restricted to apparatus of any particular shape or size. As faras the steaming tube is concerned, all that is necessary is that thegoods be heated rapidly with steam at substantially atmospheric pressureto a temperature of 212 F. or slightly below that temperature. Thus, anysteaming tube suitable for accomplishing this purpose is satisfactory,and the apertured end caps and other details of construction describedin connection with our improved apparatus may be considerably modied, oromitted, without departing from the scope of our invention. In brief,the scope of our invention is not to be restricted to procedural detailsand features set forth as illustrative of a preferred embodiment of ourimproved bleaching input process, but it is to be construed inaccordance with the appended claims and prior art.

We claim:

1. A process of bleaching textile goods which comprises impregnatingsaid goods with an aqueous alkaline solution of a peroxygen compound,rapidly heating said impregnated goods to a temperature within the range200 to 212 F, by passing them in contact with steam, and then storingsaid goods both out of contact with the main body of alkaline solutionand substantially out of contact with steam under conditions whereinheat losses are reduced but no further heat input occurs for a period ofat least thirty minutes.

2. A process of bleaching textile goods which comprises impregnatingsaid goods with an aqueous alkaline solution of hydrogen peroxide,passing said goods rapidly through a chamber lled with steam so thatsaid goods are rapidly heated to a temperature falling within the range200 to 212 F., and then storing said goods, both out of contact with themain body of alkaline solution and substantially out of contact withsteam, under conditions wherein heat losses are reduced but no furtherheat input occurs for a period of at least thirty minutes.

3. A process of bleaching textile goods which comprises thoroughlywetting said goods with an aqueous alkaline solution of a peroxygencompound, rapidly passing said wetted goods through a chamber lled withsteam under conditions wherein the temperature of the wetted textilegoods is elevated to one falling within the range 200 to 212 F., andthen storing said goods in an insulated storage chamber, both out ofcontact with the main body of alkaline solution and substantially out ofcontact with steam, so that the temperature thereof falls fromsubstantially 200 F. to substantially 170 F. during the ensuing storageperiod of at least thirty minutes.

4. A process of bleaching textile goods which comprises wetting saidgoods with an aqueous alkaline solution of hydrogen peroxide, heatingsaid goods rapidly so that the temperature is rapidly elevated to atemperature within the range 200 to 212 F. by passing said goods incontact with steam, and then storing said goods both out of contactlwith the main body of alkaline solution and substantially out of contactwith steam under conditions wherein the temperature drops tosubstantially F., for a period of time suilicient to secure satisfactorybleaching of said textile goods.

5. A process of bleaching textile goods which comprises thoroughlywetting said goods in an aqueous solution of a peroxygen compound,rapidly passing said goods through a chamber lled with steam atatmospheric pressure so that said wetted goods are heated to atemperature approximating 212 F., and then storing said goods, both outof contact with the main body of aqueous solution and substantially outof contact with steam, under conditions wherein heat losses are avoidedbut no further heat input occurs for a period of time of at least thirtyminutes during which period bleaching occurs, the temperature of saidgoods during said bleaching period progressively falling from one in theneighborhood of 200 F. to one of substantially 170 F.

6. A process of bleaching textile goods which comprises thoroughlywetting said goods in an aqueous alkaline solution of hydrogen peroxide,rapidly passing said impregnated goods through a chamber lled with steamat atmospheric pressure, and then storing said goods, both out ofcontact with the main body of alkaline solution and substantially out ofcontact with steam, under conditions wherein heat losses are reduced butno further heat input occurs for a period of time ranging from thirtyminutes to sixty minutes, during which period the temperature of saidimpregnated goods falls from one in the neighborhood of 200 F. to one inthe neighborhood of 170 F. and said hydrogen peroxide acts upon saidtextile goods to bring about bleaching thereof,

7. A continuous method for bleaching textile goods which comprisescontinuously passing a web of textile goods through an aqueous solutionof a peroxygen compound, then continuously passing said web through achamber lled with steam, said Web being in contact with said steam onlyfor a Very short period of time, during which time the temperature ofsaid web is raised to one falling Within the range 200 to 212 F., andthen continuously passing said web into an insulated compartment whereinsaid Web is stored both out of contact With the main body of aqueoussolution and substantially out of contact With steam so that thetemperature of said web drops from one of substantially 200 F. to one inthe neighborhood of 170 F., and said textile goods are bleached by theaction of said peroxygen compound.

8. A method of bleaching textile goods Which comprises the steps ofsubjecting said goods to preliminary treatment with an aqueous alkalinesolution at an elevated temperature, impregnating said goods with ableach liquor comprising an aqueous solution of a peroxygen compound,squeezing out excess bleach liquor, passing the goods in heat contactWith steam so that said goods are rapidly heated to a temperature Withinthe range 200 to 212 F., and then storing said goods both out of contactWith the main body of aqueous solution and substantially out of contactwith steam under conditions wherein the temperature is progressivelyreduced from one approximating 200 F. to one approximating 170 F., saidstored goods being stored during said period under conditions wherein noheat input thereto occurs.

DONALD J. CAMPBELL. FRANCIS LE ROY FENNELL.

MUUH

